Radioactive lenses - yikes!

[Gerald C Koch]

The radioactivity causes defects in the crystal lattice of the glass. These defects can be an atom out of place which absorbs light of a particular wavelength. The energy of the UV photons can knock the misplaced atoms back into place. Heat will also work but obviously cannot be used for lenses.

Curiously UV light can also cause coloring of glass. Old whiskey bottles found in the American desert are often amber or purple from the exposure they receive and command a higher price on the antique market.

[Newt_on_Swings]

Ah, thanks. That is really interesting, I always thought unstable elements always broke down into more stable forms over time, but I guess with enough bombardment you can knock them back. Kinda like what happens in a collider i guess.

[Gerald C Koch]

Ah, thanks. That is really interesting, I always thought unstable elements always broke down into more stable forms over time, but I guess with enough bombardment you can knock them back. Kinda like what happens in a collider i guess.

Perhaps my post wasn't as clear as it should have been. It is true that radioactive isotopes eventually decay to stable ones. The UV photons cannot effect this decay in anyway. Once an atom decays you cannot reverse the process.

Think of the atoms in the crystal lattice of the glass as marbles in the holes of a Chinese checkers board. Radiation has caused one of the atoms (marbles) to be knocked out of its hole. A UV photon can push the atom (marble) back into its hole.

Even in a throium glass the majority of atoms in the glass lattice are either silicon or oxygen atoms. For simplicity I say atoms but in actuality they are present as ions in the lattice.

[Newt_on_Swings]

Oh that makes it much clearer with that example. Science, always something new to learn!

[Soeren]

Sh** radioactive lenses. Oh my, will they fog my film?
Best regards

[Poisson Du Jour]

Funny isn't it, that early Takumar lenses are still renowned as stirling performers with a bit of thorium thrown in. Nothing to get all hot and sweaty about.

[Gerald C Koch]

Something very similar happens in a photographic emulsion. A light photon knocks a silver or halide ion out of its place in a silver halide grain. This makes what is called an activation site which is more easily reduced by a developing agent than other portions of the grain.

[Gerald C Koch]

I think too much is made of any color change caused by these lenses. Certainly BW films will not be effected. For color films there may be a slight warming of the colors. It is well known that humans tolerate any change toward a warmer hue much better than a change to a cooler one. Thus color labs prefer that slides and prints tend toward warm tones rather than cool ones and adjust their processing accordingly. We don't like it if Aunt Nellie is blue or green.

[RidingWaves]

Ive got 3 of the Nikkor 35mm 1.4 radioactive ones. One I've cleared as best I can, 3 weeks in the bright UV rich Hawaiian Sun, and one I've left in its natural yellow state, and one that is somewhat in the middle. The yellow one looks interesting in color, but looks quite nice in B&W. I use the cleared one all the time.]

Gureny-Mott!

[ErosP]

Lovely and interesting can of worms I opened up awhile back, now didn't I? LOL!

~!Eros